Subtractive color photography forms a color image by forming yellow, magenta, and cyan dyes respectively complementary to blue, green, and red, which result from the coupling of the respective yellow, magenta, and cyan dye-forming couplers with the oxidation product of an aromatic primary amine color-developing agent formed by reducing an exposed silver halide with the color-developing agent. Substantially nondiffusible couplers to be contained in photographic materials are generally dissolved in phosphate-type or phthalate-type high-boiling organic solvents substantially insoluble in water, and if desired cosolvents, and they are added to silver halide emulsions.
Nondiffusible couplers are required to have such basic properties that not only can they be developed to form dyes, but also their solubility in high-boiling organic solvents is high, their dispersibility and stability in silver halide photographic emulsions are good, and the light resistance, heat resistance, and humidity resistance of the image dyes formed therefrom are favorable.
Because the magenta dyes formed, for example, from 1H-pyrazolo[5,1-c][1,2,4]triazole-type couplers described in U.S. Pat. No. 3,725,067 and British Patent Nos. 1,252,418 and 1,334,515, 1H-pyrazolo[1,5-b][1,2,4]triazole-type couplers described in European Patent No. 119,860, 1H-pyrazolo[1,5-d]tetrazole-type couplers described in RD No. 24220 (June 1984), and 1H-pyrazolo[1,5-b]pyrazole-type couplers have less harmful subsidiary absorption near 430 nm, they are preferred in view of color reproduction, and they are also preferable in that they do not allow the color-unformed part to have yellow stain due to heat or humidity.
However, the light-fastness of the azomethine dyes formed from these couplers is low, which spoils the performance of color photographic materials, in particular print color photographic materials.
Further, these couplers have such problems that if the coupler is processed with a color developer into which a trace amount of a bleaching solution or a bleach-fix solution had accidentally been mixed during the processing thereof, resulting in an increase of the solubility of silver halides, the color-formed dye density lowers considerably and the sensitization decreased greatly.
JP-A (("JP-A" means unexamined published Japanese patent application) No. 84641/1986 describes that high-boiling chlorinated paraffins are used as coupler solvents to improve the dispersibility and the solubility in a color photographic material, to thereby improve the dye image stability. However, in this photographic material, the problem of lowering color-formed dye density due to contamination of color developer by a bleach-fix solution was not solved.
On the other hand, JP-A Nos. 65245/1986 and 89961/1987 describe that pyrazoloazole-type magenta couplers having at least one substituted-alkyl group as a substituent are improved in fastness to light and are excellent in color reproduction. However, these couplers have a defect that the process stability is poor. In particular, they have defects that even if a color developer that is not fatigued is used, when a very small amount of a bleaching solution or a bleach-fix solution (for example, one using EDTA ferric iron) is used in the color developer, the loss of the color-formed dyes is great and the color-formed dye density is reduced.